LAUSR

Simple Summary This research aimed to define intestinal DCs from myxines to teleosts by using immunohistochemistry with TLR-2, Langerin/CD207, and MHC II. In particular, we analyzed intestinal DCs in several species of fish phylogenetically organized: Eptatretus cirrhatus (myxines), Scyliorhinus canicula (Chondrichthyes), Polypterus senegalus (Osteichthyes, Brachiopterygii), Lepisosteus oculatus (Osteichthyes, Holostei), and Clarias batrachus (Osteichthyes, Teleostei). The findings show that intestinal DCs and DC-like cells are positive to all the antibodies tested, demonstrating the presence of these cells phylogenetically from myxines to teleosts. These results could improve the state-of-the-art on the evolution of the immune system and the importance of sentinel cells in the body’s defense. In addition, we demonstrated with immunohistochemistry the presence of MHC II in myxines (Eptatretus cirrhatus) for the first time. Abstract Dendritic cells (DCs) are antigen-presenting cells (APCs) that regulate the beginning of adaptive immune responses. The mechanisms of tolerance to antigens moving through the digestive tract are known to be regulated by intestinal DCs. Agnatha and Gnathostoma are descendants of a common ancestor. The Ostracoderms gave rise to Cyclostomes, whereas the Placoderms gave rise to Chondrichthyes. Sarcopterygii and Actinopterygii are two evolutionary lines of bony fishes. Brachiopterygii and Neopterygii descend from the Actinopterygii. From Neopterygii, Holostei and Teleostei evolved. Using immunohistochemistry with TLR-2, Langerin/CD207, and MHC II, this study aimed to characterize intestinal DCs, from myxines to teleosts. The findings reveal that DCs are positive for the antibodies tested, highlighting the presence of DCs and DC-like cells phylogenetically from myxines, for the first time, to teleosts. These findings may aid in improving the level of knowledge about the immune system’s evolution and these sentinel cells, which are crucial to the body’s defense.